A series of precision glycomacromolecules is prepared following previously established solid phase synthesis allowing for controlled variations of interligand spacing and the overall number of carbohydrate ligands. In addition, now also different linkers are installed between the carbohydrate ligand and the macromolecular scaffold. The lectin binding behavior of these glycomacromolecules is then evaluated in isothermal titration calorimetry (ITC) and kinITC experiments using the lectin Concanavalin A (Con A) in its dimeric and tetrameric form. The results indicate that both sterical and statistical effects impact lectin binding of precision glycomacromolecules. Moreover, ITC results show that highest affinity toward Con A can be achieved with an ethyl phenyl linker, which parallels earlier findings with the bacterial lectin FimH. In this way, a first set of glycomacromolecule structures is selected for testing in a bacterial adhesion-inhibition study. Here, the findings point to a one-sugar binding mode mainly affected by sterical restraints of the nonbinding parts of the respective glycomacromolecule.
The study of bacterial adhesion is crucial to our understanding of infection processes as well as for the development of antiadhesives. Here we have investigated new nanodiamond glycoconjugates intended to inhibit adhesion of type 1 fimbriated E. coli bacteria. For conjugation of saccharides and nanodiamond, thiourea‐bridging was employed, a method that has not been used before in nanodiamond derivatization. Amino‐prefunctionalized diamond nanoparticles were prepared employing aromatic diazonium salts and reacted with different isothiocyanato‐functionalized mannose derivatives. The resulting glyconanodiamonds were characterized and then tested in bacterial binding assays. They are recognized by the bacterial protein FimH according to the structure‐activity relationships known for this lectin. Thus, owing to the particular properties of nanodiamond, a valuable material is introduced with the potential to control bacterial adhesion and colonization in a favorable way.
Adhesion of bacteria to the glycosylated surface of their target cells is typically mediated by fimbrial lectins, exposed on the bacterial surface. Among the best-investigated and most important fimbriae are type 1 fimbriae, for which α-d-mannopyranoside-specificity has been described. This carbohydrate specificity is mediated by the type 1 fimbrial lectin FimH. In this account, we have employed four different set-ups to assay type 1 fimbriae-mediated bacterial adhesion, including tailor-made glycoarrays. The focus of our study was on testing FimH specificity with regard to the glycone part of a glycosidic ligand by testing a series of synthetic α-mannosides, as well as α-glucosides and α-galactosides. Unexpectedly, it was found that in solution all tested aminothiahexyl glycosides inhibit bacterial adhesion but that this effect is unspecific. Instead it is due to cytotoxicity of the respective glycosides at high mm concentrations.
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